Search

The emergence of high-performance antennas based modern manufacturing technology and novel additive processing is becoming a hot topic. Specifically, the substrate integrated waveguide (SIW) has demonstrated its impact in miniaturization, planarization, and low-cost manufacturing of transmission lines, while 3D printing technology has enabled the creation of customized, high-performance antennas. The research into SIW and 3D printed antennas are emergence for the advancement of wireless communication systems. In this thesis, novel millimeter-wave and microwave antennas based on modern and newly emerged additive manufacturing are investigated. First of all, in terms of novel antenna designs based on traditional manufacturing, several SIW-based planar directional antennas are presented in achieving high gain, miniaturization, easy integration and design simplification. They are i) SIW H-plane horn antenna with gradient air slots, ii) SIW H-plane horn antenna with an embedded air cavity; iii) SIW H-plane horn antenna loaded with linear dipole directors. Then, in terms of novel antenna designs based on 3D printing technologies, a variety antenna structures were proposed and studied. They are i) Fused deposition modelling (FDM) printed E-plane horn for gain enhancement; ii) Liquid crystal display (LCD) printed horn antennas for size reduction; iii) LCD printed horn antenna for beam-steering; iv) LCD printed rod antenna with modified permittivity for high gain; v) LCD printed dielectric lens for high directivity. All antenna designs including the concepts and design process presented are theoretically analyzed and introduced. They are fabricated and measured. The main contribution includes the novel antenna designs in both modern and additive manufacturing technologies for superior radiation performance and various design purposes.

Although phosphate is one of the essential nutrients for life, excess phosphate can cause negative health and environmental conditions, such as hyperphosphatemia and eutrophication. Phosphate sequestration is thus one of the most effective approaches for medical and environmental remediation. Unfortunately, current treatment is either inefficient or unsustainable. Organic phosphate receptors often fail to satisfy the most important requirement – efficacy and selectivity in water. In contrast, inorganic receptors exploit the strong phosphate-metal interaction to sufficiently overcome the hydration energy of phosphate that impedes organic receptors. In particular, lanthanide-based receptors with open coordination sites are well-suited for phosphate sequestration. Achieving selectivity for phosphate however, remains unmastered. This dissertation seeks to develop a fundamental insight into factors that underpin anion coordination to lanthanide complexes. The host-guest interaction of lanthanide-based receptors is highly dependent on the geometry of the coordination sites or the coordinated water molecules. In the first study, we demonstrated that indeed larger ligand caps favor more water molecules coordinated, while not all them can be displaced by phosphate. However, there is no direct relationship between the number of inner-sphere water molecules and affinity for coordinating anions. Next, in order to tune the binding affinity, we incorporated a charge or hydrogen bonding moiety peripherally to the metal center. The secondary interaction promoted phosphate binding, with the strongest enhancement by Coulombic interaction, followed by hydrogen bonding. Importantly, the selectivity for phosphate remained intact. The performance of the most water-soluble complex in elevated pH was further evaluated. Surprisingly, in basic condition, the europium(III) complex binds cyanide with a 9-fold turn-on luminescence. Unlike most cyanide probes that rely on reaction-based mechanism, the europium(III) complex detects cyanide based on direct coordination. Lastly, we extended our scope to less appreciated iron(III)-based receptors. The presence of a weak coordinating yet highly fluorescent dye effectively prevents ?-oxo dimer formation, and probes phosphate with turn-on fluorescence. Notably, the iron(III)-based receptors are selective over pyrophosphate and arsenate. Collectively, this dissertation demonstrates that the interplay of ligand geometry and peripheral groups can be exploited to develop selective phosphate receptors.

Optical waveguide interconnect has been considered as a key enabling technology to address bandwidth bottleneck limited by electrical wire at board levels. Current waveguide technology for optical interconnect were realized based on 2D waveguide technology based on layer-by-layer lithography schemes built on silicon or polymer substrates. As data rate explodes at chip and board levels, the optical routing complexity and high laser power required to support high data bandwidth demand a new waveguide interconnect topology. In this dissertation, we study and explore ultrafast laser fabrication technology to build highly complex 3D waveguide lightwave circuits in glass substrates to support demand for high bandwidth optical interconnect. This dissertation first explores 3D waveguide structure fabrication in flexible glass substrates. Characteristics and performances of various waveguide devices inscribed in flexible glasses are compared with those built on polymer substrates. This work is then followed by development of an integrated laser manufacturing solution, using the same platform, to manufacture board-level optical interconnect waveguides and 45° total internal reflection (TIR) micromirror for vertical coupling. To expand 3D waveguide technology in optical fiber devices, 3D waveguide couplers and WDM components, two key components for fiber lasers, were directly fabricated on multi-core optical fibers, turning the silica fiber from a 1-D optical channel to a 3-D integrated system. Based on paraxial approximation, 3D coupled photonic waveguide array were designed, fabricated, and characterized to study photonic graphene under Gauge field. Results and efforts described in this dissertation demonstrated that, through the optimization of laser matter interaction, high-density 3D waveguide consists of more than 15 layer can be fabricated for a wide array of photonic applications.

This dissertation includes three essays that examine the interactions between financial arrangements and product market outcomes in the health care industry theoretically and empirically. Integrating finance and health economic theories, particularly the coexistence of mixed ownerships and the private provision of public goods, my dissertation presents unique opportunities to explore the interaction of the fields of health care finance and industrial organization. Chapter 2 includes an evaluation of nursing home quality, which provides a valuable opportunity to clarify the cyclical fluctuation of quality and the role of financial constraints in explaining such fluctuation. As such, I use local unemployment rates to provide exogenous cost shocks. During recessions, lower labor costs ease financial constraints and thus lead to higher nurse staffing, lower employee turnover, and better quality. Such counter-cyclical quality fluctuation is most profound among financially constrained facilities that tend to be more leveraged. This counter-cyclical quality is also more pronounced among nursing homes that are for-profit, belong to multi-facility chains, and focus largely on Medicaid residents. Overall, I find that financial constraints hinder quality, nursing home quality is counter-cyclical, and financial constraints slightly amplify counter-cyclical quality fluctuations. Chapter 3 examines the impacts of financial leverage on hospitals’ technology adoptions. To account for the potential endogeneity between financing and producing decisions, the California Seismic Retrofit Mandate is used as an exogenous financial shock that crowds out hospitals’ financial resources. Surprisingly, I did not find significant results to identify the association between financial leverage and technology adoption. Using a unique 8-year nursing home CEOs’ compensation dataset, I make inferences of the objective functions of for-profit and not-for-profit organizations, particularly the differential weights of financial and altruistic (quality) performance. Surprisingly, I find that compensation is not tied to performance. Rather, managers are compensated for more concrete measures including the size of the nursing home, payer-mix, and manager experience. I further separate managers into three groups (not-for-profit managers, for-profit and owner-managers, and for-profit and non-owner managers). Among these three types of managers, I find consistently significant evidence that owner-managers earn significantly higher compensation than do the other two types of managers.

This dissertation is composed of three studies that use statistical, behavioral, and neuroimaging methods to investigate Chinese and English speakers’ semantic interpretations of four types of visual information including icons, single Chinese characters, single English words, and pictures. The goal is to examine whether people cognitively process icons as logographical words. By collecting survey data from 211 participants, the first study investigated how differently these four types of visual information can express specific meanings without ambiguity on a quantitative scale. In the second study, 78 subjects participated in a behavioral experiment that measured how fast people could correctly interpret the meaning of these four types of visual information in order to estimate the differences in reaction times needed to process these stimuli. The third study employed functional magnetic resonance imaging (fMRI) with 20 participants selected from the second study to identify brain regions that were needed to process these four types of visual information in order to determine if the same or different neural networks were required to process these stimuli. Findings suggest that 1) similar to pictures, icons are statistically more ambiguous than English words and Chinese characters to convey the immediate semantics of objects and concepts; 2) English words and Chinese characters are more effective and efficient than icons and pictures to convey the immediate semantics of objects and concepts in terms of people’s behavioral responses, and 3) according to the neuroimaging data, icons and pictures require more resources of the brain than texts, and the pattern of neural correlates under the condition of reading icons is different from the condition of reading Chinese characters. In conclusion, icons are not cognitively processed as logographical words like Chinese characters although they both stimulate the semantic system in the brain that is needed for language processing. Chinese characters and English words are more evolved and advanced symbols that are less ambiguous, more efficient and easier for a literate brain to understand, whereas graphical representations of objects and concepts such as icons and pictures do not always provide immediate and unambiguous access to meanings and are prone to various interpretations.